Stone structures, monuments and the like, hereinafter designated for the sake of simplicity as structures, are subjected in the course of years to a constant exposure to the atmosphere. The surface of the structures is constantly exposed to the harmful substances contained in the atmosphere, such as carbon dioxide, carbon monoxide, sulfur dioxide, nitrogen oxides etc., along with the moisture deposited by rain and fog. Dirt is deposited in the pores and together with metabolic products produced by the microorganisms, and the stone texture of the structure is destroyed, thus bringing about a more or less rapid erosion of the stone material used in the structure.
In the course of the years, this results in a continuously progressing destruction of the structure.
In the case of historical structures, monuments and the like, in particular, this continuous process of destruction proves to be extremely unpleasant because irreplaceable assets are always lost as a result.
Great efforts have already been made to stop this process of destruction and, in addition, to renovate the damage which has already occurred.
For this purpose, stone materials are treated with solutions of silicic-acid ester. A part of its natural binder is therefore returned to the stone.
This known silicic-acid ester method is, however, applicable to lime-bound materials only to a limited extent.
In addition, a further disadvantage can be seen in the fact that the pores present in the stone material are largely sealed so that the natural breathing of the stone material is impaired by the treatment.